The question of language labs recently came up on an independent school listserv, and as a French teacher/Director of Edtech, I felt compelled to respond. I strongly believe that language labs are a waste of precious resources, both in terms of budgets and facilities. Here's why:
Integrate, not isolate
The idea of a separate lab runs counter to the idea of integrating tech into the everyday curriculum. Just as we've abandoned the isolated computer lab for more ubiquitous 1:1 or BYOD models, having to book a language lab and manage the hassle of getting students there and setting up/breaking down will limit the number of speaking/listening activities that teachers undertake. This is a bad idea for a communicative based language program. Speaking and listening activities need to take place as much as possible, both in school as well as home for homework. It is extremely counterintuitive for speaking activities to be recorded one way at school and then through another program at home. I'd suggest headsets for students paired with one of the options in #2 below. We keep our headsets in the classrooms in a cabinet. Students know where they are and how to set them up, creating an efficient workflow transitioning into and out of listening/speaking activities.
There are so many amazing options for recording and sharing sound files that are a fraction of the financial and facilities cost of a language lab. Dedicating an entire room to equipment that is occasionally used is a waste of space. Most textbooks now have an online component that allow students to listen and record their voice, as well as having voice based discussion boards. I used VHL and it was fantastic. If not the text, then your LMS will probably have excellent recording capabilities. At my former school Moodle had this functionality, and in my current one, Canvas has an even better and easier system. If neither text nor LMS, then there are great free Web 2.0 tools to check out. Audacity has been mentioned already, if you're a Mac school, Garage Band comes standard. Google Drive has voice recorder apps that are decent and easy to use. Finally, a free ridiculously easy cloud option is Vocaroo. Pushing video content to students is also easy with the plethora of options, including Youtube, Vimeo, Teachertube, etc.
The synchronous/asynchronous argument is a moot point. If your listening file is embedded into a website/discussion prompt/voiceboard, the activity and subsequent student responses will be as synchronous as a traditional listening lab. A good headset with mic isolates the students' voices so that only their response is recorded. If the idea of teacher synchronous listening is the issue, having the teacher walk around and listen to individual students performs the same function. (Protest: Having the teacher next to the student makes them nervous, anonymous listening is better! Response: Get over it! Our job is to prepare students for authentic communicative situations. Having a speaker next to them is much more authentic than being isolated in a booth!)
Overcoming resistance to change
Changing from a system where the teacher has all of the control and students are neatly organized into tidy booths to a classroom-based anytime system can be intimidating. That's where good edtech coaching and leadership comes in. As technology administrators it is our job to set up the systems as best as we can so that they are as easy as possible for our teachers to use. We also need to logically explain the benefits to teaching and learning that will result from abandoning an archaic methodology such as a language lab. But sometimes we also need to console, reassure, and cheer on our colleagues as they take coerced leaps of faith into the unknown.